TMF Introduction (G06.26+)

Transaction Coordination
HP NonStop TMF Introduction—522414-002
2-4
How Distributed Transaction Coordination Works
Transaction gateways translate between one protocol and another; they translate
imported transactions and transaction IDs to the local protocol, and translate exported
transactions and transaction IDs to the remote protocol. The transaction manager
using a gateway does not need to know the characteristics of the object it is
communicating with at the other end of the gateway; it only needs to know that the
object follows the protocol supported by the gateway. You can think of the object at the
other end of the gateway as a “black box,” or unknown object as shown in Figure 2-2;
TMF makes no assumptions about what the object is.
How Distributed Transaction Coordination Works
Although multiple transaction managers are involved in distributed transactions, one
transaction manager must be responsible for determining whether to commit or abort
the transaction for all participants. This transaction manager is called the commit
coordinator; it coordinates with the other participants to commit or abort the
transaction.
The commit coordinator is the transaction manager that initiates the transaction. The
commit coordinator acts as the parent or superior transaction manager (as shown in
Figure 2-3) and records the other child or subordinate systems involved in the
transaction. Parent nodes send transactions; child nodes receive transactions. By
recording these nodes, the commit coordinator can make sure the transaction is
eventually committed or backed out on all participating nodes.
Figure 2-2. A Transaction Gateway
Transaction
Gateway
Transactions
TMF
“Black Box”
Remote TM
or RM
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